The characterization of the process of separating cellulose fibers from wood by using L-lactic acid was investigated. Sugi (Cryptmeria Japonica) were cooked with L-lactic acid at 200 degrees C for 1 hr to be separated as pulp-like fibers and liquefied wood components. The pulp-like fibers were analyzed with molecular weight, SEM, X Ray diffractions, IR and C-13 NMR. Molecular weight was about 1.1 x 10(6) Mix 10(6). The crystals of the pulp-like fibers were type 1 and the crystallinity was 23-25%. The pulp-like fibers were esterified with L-lactic acid. It was concluded that the cooking the wood with L-lactic acid was a significant separation system, taht the delignification occurred by acid hydrolysis and decomposition, and that esterified cellulose derivatives were produced from wood material.